Configurations of V4+ centers in the MoVO catalyst material. A systematic stability analysis of DFT results

The reactivity of a catalyst is in part determined by its geometric and electronic structure. Here we present a model that is able to describe the energy trend of the important oxidation catalyst material MoVO, as obtained from hybrid density functional calculations for various V4+/V5+ configurations. For an exemplary V/Mo occupancy, we systematically examined the universe of all V4+ distributions. The distribution of these V4+ centers, in combination with the induced lattice distortions, plays a key role in determining the stability of the material, entailing energy variations of up to ~140 kJ mol−1 per unit cell. Hence, for this kind of catalyst, it is crucial to account for the V4+ distributions. To this end, we are proposing novel predictive models based on features like the number of Mo centers with two reduced neighbors V4+ and the locations of potentially reducible centers V5+. For the V/Mo occupancy chosen, these models are able to describe the energy variation due to the V4+ distribution with root mean square errors as low as 6 kJ mol−1. Accordingly, catalytically selective sites featuring pentameric units with a single polaron center are among the most of stable configurations. Another aspect of this work is to understand energy contributions of polaron arrangements bracketing Mo centers

Comment on “First-principles-based embedded atom method for PdAu nanoparticles”

International audienceBin Shan et al. developed an embedded-​atom-​model potential for studying structural properties of Pd​/Au alloy nanoparticles by means of Monte Carlo simulations. The parameters reported for the Pd-​Au pairwise interaction appear to be erroneous as the Pd-​Au interaction potential, Fig. 5(c) of that publication, cannot be reproduced with those parameters. In this Comment, we use the same procedure and ref. systems for parametrization to provide a cor. set of parameters and we demonstrate, for selected results, that the previously published calcd. properties of Pd​/Au nanoparticles appear to be correct

The origin of the particle-size-dependent selectivity in 1-butene isomerization and hydrogenation on Pd/Al2O3 catalysts

The selectivity of 1-butene hydrogenation/isomerization on Pd catalysts is known to be particle size dependent. Here we show that combining well-defined model catalysts, atmospheric pressure reaction kinetics, DFT calculations and microkinetic modeling enables to rationalize the particle size effect based on the abundance and the specific properties of the contributing surface facets.We gratefully acknowledge financial support by the Austrian Science Fund (FWF; Single Atom Catalysis I4434-N; SFB FOXSI F4502-N16), MEC (Acciones Integradas HU2006-002) and ÖAD (WTZ 12/2006). JSA acknowledges GV (BEST/2007/045) supporting research stays in Vienna. This work was supported by grants 1527700033, A19E9a0103 of the A*STAR Science and Engineering Research Council, as well as a generous allotment of computational resources at the A*STAR Computational Resource Center, the National Supercomputing Centre Singapore and the Vienna Scientific Cluster (VSC)